Microwave photonic mirror frequency rejection mixing chip and mixing method

Abstract

This invention discloses a microwave photonic image suppression mixer chip and mixing method. The chip integrates a grating coupler, a 1×2 MMI, two single-input dual-output single-ended push-pull silicon-based carrier depletion modulators, two 2×2 MMIs, and two GeSi balanced photodetectors. This scheme, based on a single dual-parallel modulator structure combined with a balanced detector structure, can achieve both orthogonal intermediate frequency (IF) signal output and image suppression. The system structure is simple and highly stable. It eliminates the need for a narrowband optical bandpass filter, resulting in a large system operating bandwidth. By employing a balanced detector structure, the system's relative intensity noise and RF leakage terms are suppressed, while the output IF term gain is increased, leading to a higher system signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to the field of microwave photonics technology, specifically to a microwave photonics mirror frequency suppression mixer chip and mixing method. Background Technology

[0002] Microwave mixers convert signals to different frequencies and are the basic functional unit of microwave systems. In transmitters, intermediate frequency (IF) signals need to be up-converted to electromagnetic frequencies suitable for wireless transmission using a mixer; in receivers, microwave mixers down-convert the radio frequency (RF) signals carrying information received by the antenna to IF or baseband for signal processing. As electronic systems continue to evolve towards higher frequencies, larger bandwidths, greater dynamic range, and multifunctional integration, traditional microwave mixing technology faces electronic bottlenecks such as limited bandwidth, poor frequency tunability, poor isolation, and severe electromagnetic interference, making it difficult to meet the needs of future electronic systems. Compared to electrical microwave mixers, microwave-photonic mixers modulate microwave signals into the optical domain, utilizing the broadband advantages of photonic devices to achieve frequency conversion of microwave signals. They offer advantages such as high-frequency processing capabilities, large instantaneous bandwidth, low frequency-dependent loss, resistance to electromagnetic interference, and integrability, making them a promising candidate for broadband radio frequency information systems.

[0003] Due to the complexity of the electromagnetic environment in space, the signal received by the antenna at the mixer module receiver includes not only the radio frequency (RF) signal carrying information but also many other frequency components, including image frequency (IM) signals. Mixers based on heterodyne structures are highly susceptible to interference from image frequency signals. The resulting down-converted signal may contain both the desired signal component and unwanted image interference. Furthermore, because they are at the same frequency, they can cause aliasing in the frequency domain and become unable to recognize each other, which can even lead to distortion of the desired down-converted signal.

[0004] Image rejection mixers can suppress interference caused by image signals and maintain or enhance the power of the desired down-converted signal. One main method for achieving image rejection is phase cancellation, which involves generating two orthogonal intermediate frequency (IF) signals and introducing an additional 90° phase difference into a low-frequency 90° bridge. This ensures that the down-converted IF signals have the same phase, while the down-converted signals generated by the IM signal have opposite phases. Therefore, the image rejection interference in the down-converted signal is suppressed after the outputs are summed.

[0005] Currently, the implementation schemes of microwave photonic mirror frequency suppression mixers mainly include methods based on single-sideband carrier suppression modulation combined with 90° optical mixers, modulator bias voltage phase shift, or polarization modulator polarization shift combined with narrowband optical bandpass filters. However, these schemes mainly have the following problems: (1) The single-sideband carrier suppression modulation scheme is mostly based on multiple dual-parallel modulator structures, which requires precise control of multiple bias voltages to achieve quadrature phase shift, resulting in high system complexity and system stability being easily affected by bias voltage drift; (2) The scheme using a dual-polarization dual-parallel modulator structure and using a polarization controller to control phase shift is easily affected by polarization drift; (3) Since broadband bandpass steep optical bandpass filters are difficult to implement, the scheme using narrowband bandpass optical filters will limit the operating frequency range of the system; (4) Most existing schemes are based on discrete optoelectronic devices, such as the scheme disclosed in the patent document with application publication number CN110912614A, which has a significant gap in size and reliability compared with highly integrated electrical mixers. Therefore, there is an urgent need for miniaturization and integration of microwave photonic mirror frequency suppression mixers, while improving the reliability and stability of the system.

[0006] Currently, silicon-on-insulator (SOI) is a relatively mature photonic integration platform that can integrate passive devices, electro-optic modulators, detectors, etc. Furthermore, the SOI technology platform is compatible with CMOS processes, allowing for the monolithic integration of various functional photonic and electronic devices on a single SOI wafer. Therefore, utilizing the SOI platform to monolithically integrate modulators, optocouplers, photodetectors, etc., at the chip level, and realizing silicon-based integrated microwave photonic image suppression mixer chips, applied to image suppression microwave photonic mixing technology, can significantly improve system integration and stability.

[0007] Chinese invention patent application CN114285480A discloses a silicon-based integrated microwave photonic downconversion chip and its downconversion method. It integrates a grating coupler, two silicon-based phase modulators, a thermo-optical phase shifter, a 2×2 3dB optical coupler, and a GeSi balanced photodetector on an SOI platform compatible with CMOS technology. It uses two silicon-based phase modulators to achieve downconversion of microwave photonic signals and adopts balanced difference frequency detection. The two photocurrent signals are subtracted, and some noise and DC terms are canceled out. However, this scheme only achieves the downconversion function and does not achieve the image frequency suppression function. Summary of the Invention

[0008] The purpose of this invention is to provide a microwave photonic mirror suppression mixer chip and mixing method to solve the problems of large size, poor system stability, high scheme complexity, and limited operating frequency of the existing mirror suppression microwave photonic mixer system based on discrete devices.

[0009] The present invention solves the above-mentioned technical problems through the following technical means:

[0010] On one hand, a microwave photonic mirror frequency suppression mixer chip is proposed. The mixer chip is based on the SOI photonic integration platform and integrates a grating coupler, a 1×2 multimode coupling interferometer, an I-channel modulator, a Q-channel modulator, a 2×2 multimode coupling interferometer, a 2×2 multimode coupling interferometer, a GeSi balanced photodetector, and a GeSi balanced photodetector. The I-channel modulator and the Q-channel modulator each include a 1×2 multimode coupling interferometer, an upper phase-shifting arm, a lower phase-shifting arm, and a thermal phase shifter.

[0011] The input of the grating coupler is an optical radio frequency signal. The output of the grating coupler is connected to the first 1×2 multimode coupled interferometer via an optical waveguide. The two outputs of the first 1×2 multimode coupled interferometer are respectively connected to the inputs of the second 1×2 multimode coupled interferometer in the I-channel modulator and the Q-channel modulator. The output of each second 1×2 multimode coupled interferometer is respectively connected to the upper phase-shifting arm and the lower phase-shifting arm. The upper phase-shifting arm is connected to the thermal phase shifter. The thermal phase shifter and the lower phase-shifting arm in the I-channel modulator are respectively connected to the two inputs of the first 2×2 multimode coupled interferometer. The thermal phase shifter and the lower phase-shifting arm in the Q-channel modulator are respectively connected to the two inputs of the second 2×2 multimode coupled interferometer. The two outputs of the first 2×2 multimode coupled interferometer are respectively connected to the two inputs of the first GeSi balanced photodetector. The two outputs of the second 2×2 multimode coupled interferometer are respectively connected to the two inputs of the second GeSi balanced photodetector.

[0012] Furthermore, both the I-channel modulator and the Q-channel modulator are silicon-based single-ended push-pull carrier depletion modulators, and their electrode structures adopt a GS coplanar stripline traveling wave electrode structure, including a ground electrode G, a signal electrode S, and a DC electrode, wherein the DC electrode is located between the ground electrode G and the signal electrode S.

[0013] Secondly, a microwave photonic mirror frequency suppression mixing method is also proposed. The method for implementing mirror frequency suppression mixing using the aforementioned microwave photonic mirror frequency suppression mixing chip is as follows:

[0014] The optical radio frequency signal carried in the optical fiber is coupled into the photonic mixer chip through the grating coupler, and after being split into equal power by the 1×2 multimode coupling interferometer, it is input into the I-channel and Q-channel modulators respectively.

[0015] A DC bias voltage is applied to the DC electrodes of the I-channel modulator and the Q-channel modulator so that both modulators operate in a carrier depletion state; the thermo-optic phase shifters in the I-channel modulator and the Q-channel modulator are controlled so that both modulators operate at the maximum transmission point.

[0016] The local oscillator signal is split into two local oscillator signals with the same amplitude and a 90° phase difference by an off-chip 90° bridge. These signals are then loaded onto the signal electrodes of the two modulators to modulate the local oscillator signal onto the optical radio frequency signal and output to the 2×2 multimode coupling interferometer one and the 2×2 multimode coupling interferometer two.

[0017] The GeSi balanced photodetector one and the GeSi balanced photodetector two respectively beat the radio frequency signal modulated on the optical carrier output by the corresponding 2×2 multimode coupled interferometer with the local oscillator signal, and output I-channel down-converted signal and Q-channel down-converted signal, with the I-channel and Q-channel down-converted signals being orthogonal to each other.

[0018] The I-channel downconverted signal and the Q-channel downconverted signal are combined into a single combined signal using an off-chip low-frequency 90° bridge. Then, the high-frequency terms in the combined signal are filtered out by an electrical low-pass filter to obtain an intermediate frequency signal with suppressed image frequency signal.

[0019] The advantages of this invention are:

[0020] (1) The output of orthogonal intermediate frequency signals and image frequency suppression can be achieved based on a single dual parallel modulator structure without the need for complex multiple bias point control and polarization control. The system structure is simple and highly stable. By using GeSi balanced photodetectors, the two photocurrent signals are subtracted, the relative intensity noise and RF leakage of the laser input are suppressed, and the gain of the output intermediate frequency term is increased, thus increasing the system signal-to-noise ratio. After the output signals of the two GeSi balanced photodetectors are combined into one beam through an off-chip low-frequency 90° bridge, the intermediate frequency obtained by downconversion of the Q-channel image frequency signal and the intermediate frequency generated by the I-channel image frequency are out of phase and cancel each other out, thus achieving image frequency suppression. Moreover, the mixer chip does not need to use a narrowband optical bandpass filter, which allows the system to operate at a larger operating bandwidth.

[0021] (2) The designed photonic mixer chip can directly downconvert optical radio frequency signals into intermediate frequency signals, and is compatible with microwave photonic radio frequency front-end systems. It has great application potential in fields such as optically controlled phased array radar and wireless communication.

[0022] (3) Based on the SOI photonics platform, this chip integrates a grating coupler, 1×2 MMI, two single-input dual-output single-ended push-pull silicon carrier depletion modulators, two 2×2 MMIs, and two GeSi balanced photodetectors, realizing the chip-based implementation of the image frequency suppression microwave photonic mixing system. It is small in size and highly integrated, and solves the problems of large size, poor system stability, high scheme complexity, and limited operating frequency of the image frequency suppression microwave photonic mixing system based on discrete devices.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a microwave photonic mirror frequency suppression mixer chip proposed in an embodiment of the present invention;

[0025] Figure 2 This is a link diagram of the image frequency suppression downconversion implementation of the mixer chip proposed in this embodiment of the invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown in the figure, this embodiment of the invention proposes a microwave photonic mirror frequency suppression mixer chip. The mixer chip integrates a grating coupler 10, a 1×2 multimode coupling interferometer 20, an I-channel modulator 30, a Q-channel modulator 40, a 2×2 multimode coupling interferometer 50, a 2×2 multimode coupling interferometer 60, a GeSi balanced photodetector 70, and a GeSi balanced photodetector 80 based on an SOI photonic integration platform. The I-channel modulator 30 and the Q-channel modulator 40 each include a 1×2 multimode coupling interferometer 1, an upper phase-shifting arm, a lower phase-shifting arm, and a thermal phase shifter 2.

[0028] The input of the grating coupler 10 is an optical radio frequency signal. The output of the grating coupler 10 is connected to the 1×2 multimode coupled interferometer 20 via an optical waveguide. The two outputs of the 1×2 multimode coupled interferometer 20 are respectively connected to the inputs of the two 1×2 multimode coupled interferometers 1. The output of each 1×2 multimode coupled interferometer 1 is respectively connected to the upper phase-shifting arm and the lower phase-shifting arm. The upper phase-shifting arm is connected to the thermal phase shifter 2. The thermal phase shifter 2 and the lower phase shifter 2 in the I-channel modulator 30 are also connected to the intermode modulator 30. The arms are respectively connected to the two input terminals of the 2×2 multimode coupled interferometer 50, the thermal phase shifter 2 and the lower phase shifter arm in the Q-channel modulator 40 are respectively connected to the two input terminals of the 2×2 multimode coupled interferometer 60, the two output terminals of the 2×2 multimode coupled interferometer 50 are respectively connected to the two input terminals of the GeSi balanced photodetector 70, and the two output terminals of the 2×2 multimode coupled interferometer 60 are respectively connected to the two input terminals of the GeSi balanced photodetector 80.

[0029] Furthermore, both the I-channel modulator 30 and the Q-channel modulator 40 are silicon-based single-ended push-pull carrier depletion modulators, and their electrode structures adopt a GS coplanar stripline traveling wave electrode structure, including a ground electrode G, a signal electrode S, and a DC electrode.

[0030] It should be noted that the electrode set in this embodiment is a GS electrode, which is different from the traditional GSG electrode and GGSSG electrode. The GS electrode has a simple structure and occupies a smaller chip area. The mixer chip in this embodiment uses two parallel modulators, and the GS electrode structure is more advantageous.

[0031] Specifically, in a microwave photonic link, the radio frequency signal received by the antenna first needs to be modulated into the optical domain by the modulator of the microwave photonic radio frequency front-end. The photonic mixer chip can directly demodulate and downconvert the optical radio frequency signal into an intermediate frequency signal, which is compatible with the microwave photonic radio frequency front-end system and has great application potential in fields such as optically controlled phased array radar and wireless communication. The grating coupler 10 is used to couple the received optical radio frequency signal from the optical fiber into the chip. After being split by a 1×2MMI equal-power beam, the signals enter the I-channel modulator 30 and the Q-channel modulator 40 respectively. The local oscillator signal input to the chip is split into two orthogonal local oscillator signals by a 90° bridge 90. One signal is loaded onto the signal electrode of the I-channel modulator 30, and the other signal is loaded onto the signal electrode of the Q-channel modulator 40. The I-channel modulator 30 and the Q-channel modulator 40 are used to modulate the orthogonal local oscillator signals onto the input optical radio frequency signal, realizing the electro-optic conversion of the local oscillator signal. The thermal phase shifters 2 of the I-channel modulator 30 and the Q-channel modulator 40 are used to control the I-channel modulator 30 and the Q-channel modulator 40 to operate at the maximum transmission point. The 2×2MMI I and 2×2MMI II are used to introduce a π phase difference at the two output terminals. The GeSi balanced detector is used to beat the radio frequency and local oscillator signal modulated on the optical signal and down-convert the frequency to an intermediate frequency signal.

[0032] This embodiment integrates a grating coupler, a 1×2 MMI, two single-input dual-output single-ended push-pull silicon carrier depletion modulators, two 2×2 MMIs, and two GeSi balanced photodetectors based on the SOI photonics platform. This achieves chip-based imaging frequency suppression microwave photonic mixing system with small size and high integration. It solves the problems of large size, poor system stability, high scheme complexity, and limited operating frequency of imaging frequency suppression microwave photonic mixing systems based on discrete devices.

[0033] In addition, such as Figure 2 As shown in the figure, this invention also proposes a microwave photonic mirror frequency suppression mixing method. The mixing method for mirror frequency suppression using the microwave photonic mirror frequency suppression mixing chip includes the following steps:

[0034] 1) The optical radio frequency signal received from the microwave photonic radio frequency front end is coupled from the optical fiber into the chip through the grating coupler on the chip, and after being split into equal power by a 1×2 multimode coupling interferometer, it enters the I-path and Q-path modulators respectively.

[0035] 2) Apply DC bias voltage to the DC electrodes of the I-channel and Q-channel modulators respectively, so that both modulators operate in the carrier depletion state. Control the thermo-optical phase shifters of the I-channel modulator and the Q-channel modulator so that both modulators operate at the maximum transmission point. The local oscillator signal is split into two local oscillator signals with the same intensity and a 90° phase difference through an off-chip 90° bridge. These signals are applied to the signal electrodes of the I-channel and Q-channel modulators respectively, thereby modulating the local oscillator signal onto the optical radio frequency signal.

[0036] 3) The modulated optical signals output from the I-channel and Q-channel modulators are coupled by the 2×2 multimode coupling interferometer one and the 2×2 multimode coupling interferometer two, respectively, and then input to the GeSi balanced photodetector one and the GeSi balanced photodetector two. The GeSi balanced photodetector one and the GeSi balanced photodetector two beat the corresponding radio frequency signal modulated on the optical carrier with the local oscillator signal, respectively, and output the I-channel down-converted signal and the Q-channel down-converted signal, respectively. The I-channel and Q-channel down-converted signals are orthogonal to each other.

[0037] 4) The down-converted signals of the I-channel and the Q-channel are combined into one channel through an off-chip low-frequency 90° bridge. After the high-frequency terms are filtered out by an electrical low-pass filter, an intermediate frequency signal with suppressed image frequency signal is obtained.

[0038] The following formula derivation further illustrates the mirror frequency suppression mixing principle of the microwave photonic mirror frequency suppression mixer chip proposed in this invention.

[0039] Let the optical carrier signal be E. in (t)=E c e jwct The radio frequency signal is υ RF (t)=V RF sin(ω RF t), the local oscillator signal is υ LO (t)=V LO sin(ω LO t), where E c V RF V LO The amplitudes ω represent the optical carrier signal, radio frequency signal, and local oscillator signal, respectively. c ω RF ω LO These represent the frequencies of the optical carrier signal, radio frequency signal, and local oscillator signal, respectively; assuming that the half-wave voltage of the modulators involved is the same, V.π And V LO =V RF Then the modulation coefficients of both the radio frequency signal and the local oscillator signal are β = πV. RF / V π .

[0040] The radio frequency signal received by the remote antenna is first modulated onto the optical domain by a modulator, and the resulting optical radio frequency signal can be expressed as:

[0041]

[0042] The front-end optical radio frequency (RF) signal is transmitted to the processing back-end via optical fiber. The RF signal is coupled into the designed microwave photonic mixer chip via a grating coupler. After being split by a 1×2 multimode coupled interferometer with equal power, it enters the I-path and Q-path modulators respectively. The local oscillator signal is split into two orthogonal local oscillator signals by the 90° bridge, which are respectively loaded onto the signal electrodes of the two modulators to modulate the RF signal onto the optical carrier signal. The modulated optical signal output from the upper and lower arms of the I-path modulator is expressed by the following formula:

[0043]

[0044]

[0045] The modulated optical signals output from the upper and lower arms of the Q-channel modulator are expressed by the following formula:

[0046]

[0047]

[0048] In the formula: ω RF ω LO , respectively, represent the frequencies of the optical radio frequency signal and the local oscillator signal; β is the modulation coefficient of the optical radio frequency signal and the local oscillator signal, where the optical radio frequency signal is...

[0049] In the embodiment, E I_MZM1 E I_MZM2 The modulated optical signals are input to the two input ports of the I-channel 2×2 multimode coupler, and the expressions for the modulated optical signals output from the two output ports of the 2×2 multimode coupler are as follows:

[0050]

[0051]

[0052] In the embodiment, E Q_MZM1 E Q_MZM2The modulated optical signals are input to the two input ports of the Q-channel 2×2 multimode coupled interferometer II, respectively. The expressions for the modulated optical signals output from the two output ports of the 2×2 multimode coupled interferometer II are as follows:

[0053]

[0054]

[0055] In the embodiment, E I_MMI1 E I_MMI2 The photocurrents are respectively input into GeSi balanced photodetector one, and the photocurrents output by the two detectors in GeSi balanced photodetector one are:

[0056]

[0057]

[0058] η is the responsivity of the GeSi balanced photodetector. The photocurrents of the two detectors in GeSi balanced photodetector one are subtracted. Therefore, the photocurrent output by GeSi balanced photodetector one (channel I) is:

[0059]

[0060] In the embodiment, E Q_MZM1 E Q_MZM2 The photocurrent is input to the Q-channel GeSi balanced photodetector II via a 2×2 MI input. After balanced detection, the output photocurrent of the Q-channel GeSi balanced photodetector II can be expressed as:

[0061]

[0062] In this embodiment, the photocurrent i output by the balanced detection of the I-channel and Q-channel is... I_BPD i Q_BPD After being synthesized into a single signal by a low-frequency 90° bridge circuit, this bridge introduces an additional 90° phase into the Q-channel intermediate frequency signal. The output signal of the bridge is then filtered out by an electrical low-pass filter to remove the ω. LO t、ω RF t+ω LO If high-frequency terms such as t are included, the output electrical signal can be expressed as:

[0063] i out =ηP0J1 2 (β)sin(ω RF t-ω LO t)

[0064] The frequency of the radio frequency signal to be down-converted is expressed as ω. RF =ω LO +ω IF The frequency of the image frequency signal can then be expressed as ω.IM =ω LO -ω IF After balanced detection of the I and Q channels, the down-converted output of the image frequency signal can be expressed as:

[0065]

[0066] Among them, i I_BPD For I-channel photocurrent signals, i Q_BPD η is the Q-channel photocurrent signal, η is the responsivity of the GeSi balanced photodetector, P0 is the input optical carrier power, and J1(β) is the first-type Bessel function.

[0067] i I_BPD_IM For I-channel mirror frequency signal down-converted signal, i Q_BPD_IM For the Q-channel mirror frequency signal, the down-converted signal is ω. IF_IM η represents the intermediate frequency signal generated by the mirror frequency, η is the responsivity of the GeSi balanced photodetector, P0 is the input optical carrier power, and J1(β) is the Bessel function of the first kind.

[0068] As can be seen from the above formula, after the two signals are combined into one output through a 90-degree bridge, the intermediate frequency obtained by downconverting the Q-channel image frequency signal and the intermediate frequency generated by the I-channel image frequency are out of phase and cancel each other out, thus achieving the image frequency suppression function.

[0069] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0070] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A microwave photonic mirror frequency rejection mixing chip, characterized in that, The mixer chip, based on the SOI photonic integration platform, integrates a grating coupler, a 1×2 multimode coupling interferometer, an I-channel modulator, a Q-channel modulator, a 2×2 multimode coupling interferometer, a 2×2 multimode coupling interferometer, a GeSi balanced photodetector, and a GeSi balanced photodetector. Both the I-channel and Q-channel modulators include a 1×2 multimode coupling interferometer, an upper phase-shifting arm, a lower phase-shifting arm, and a thermal phase shifter. The input of the grating coupler is an optical radio frequency signal. The output of the grating coupler is connected to the first 1×2 multimode coupled interferometer through an optical waveguide. The two outputs of the first 1×2 multimode coupled interferometer are respectively connected to the inputs of the second 1×2 multimode coupled interferometer in the I-channel modulator and the Q-channel modulator. The output of each second 1×2 multimode coupled interferometer is respectively connected to the upper phase-shifting arm and the lower phase-shifting arm. The upper phase-shifting arm is connected to the thermal phase shifter. The thermal phase shifter and the lower phase shifter arm in the I-channel modulator are respectively connected to the two input terminals of the first 2×2 multimode coupled interferometer. The thermal phase shifter and the lower phase shifter arm in the Q-channel modulator are respectively connected to the two input terminals of the second 2×2 multimode coupled interferometer. The two output terminals of the first 2×2 multimode coupled interferometer are respectively connected to the two input terminals of the first GeSi balanced photodetector. The two output terminals of the second 2×2 multimode coupled interferometer are respectively connected to the two input terminals of the second GeSi balanced photodetector.

2. The microwave photonic mirror frequency rejection mixing chip of claim 1, wherein, Both the I-channel modulator and the Q-channel modulator are silicon-based single-ended push-pull carrier depletion modulators. Their electrode structures adopt a GS coplanar stripline traveling wave electrode structure, including a ground electrode G, a signal electrode S, and a DC electrode, with the DC electrode located between the ground electrode G and the signal electrode S.

3. A microwave photonic mirror frequency rejection mixing method, characterized in that, The microwave photonic image suppression mixer chip according to any one of claims 1-2 is used to implement image suppression mixing, including: The optical radio frequency signal is input through the grating coupler, and after being split into equal power beams by the 1×2 multimode coupling interferometer, the optical radio frequency signal is input into the I-channel modulator and the Q-channel modulator respectively. A DC bias voltage is applied to the DC electrodes of the I-channel modulator and the Q-channel modulator so that both modulators operate in a carrier depletion state; and the thermo-optic phase shifters in the I-channel modulator and the Q-channel modulator are controlled so that both modulators operate at the maximum transmission point. The local oscillator signal is split into two local oscillator signals with the same amplitude and a 90° phase difference by an off-chip 90° bridge. These signals are then loaded onto the signal electrodes of the two modulators to modulate the local oscillator signal onto the optical radio frequency signal and output to the 2×2 multimode coupling interferometer one and the 2×2 multimode coupling interferometer two. The GeSi balanced photodetector one and the GeSi balanced photodetector two respectively beat the radio frequency signal modulated on the optical carrier output by the corresponding modulator with the local oscillator signal, and output I-channel down-converted signal and Q-channel down-converted signal. The I-channel downconverted signal and the Q-channel downconverted signal are combined into a single combined signal through the external 90° bridge. The high-frequency terms in the combined signal are then filtered out by an electrical low-pass filter to obtain an intermediate frequency signal with suppressed image frequency signal.

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